Aronian decides to exploit Black's move order. Taking the knight to g3 or f4 and then completing development is also playable.
6... f8g7  7. g1e2  7... a7a6  8. a2a4 This is useful to prevent …b7-b5 after an exchange of pawns on d5. 8... d8e7 A new move. To be honest, I don't quite understand what advantage Black has in delaying the inevitable moves that are the exchange on d5 or 0-0.